1. Field of the Invention
The present invention relates to a liposuction device comprising a suction cannula provided for sucking in subcutaneous fat through an entry aperture, the cannula having a longitudinal axis and being mounted on a mechanical drive member having an input provided for connecting an energy source and for producing and transmitting a movement to said cannula.
2. Description of the Related Art
The technique itself of liposuction is known as such. The suction cannula is provided to be introduced under the skin of the patient. The cannula is driven to the zone where the fat must be sucked in. The suction of the fat itself is accompanied with a repeated backward and forward motion and with a depression created inside the cannula.
To assist the user during the liposuction, apparatus with mechanical assistance have been developed provided with a mechanical drive member for producing and transmitting a movement to the cannula. In these devices, such as for example described in U.S. Pat. No. 5,348,535, the produced movement is a translation movement applied to a scrape member. In order to guide the translation movement from this member, these devices comprise an inner cannula sliding within an outer guiding cannula. The outer cannula is thus provided for guiding the translation movement from the inner cannula, whereas the inner cannula serves as suction cannula.
The drawback of the device according to U.S. Pat. No. 5,438,535 is that the translation movement of the inner cannula with respect to the outer cannula provokes a xe2x80x9cguillotinexe2x80x9d or cutting effect, i.e. it may provoke the cut of the vessels and the nerves. This guillotine effect almost necessarily imposes a general anesthesia of the patient. Furthermore, the fat risks to infiltrate between the inner cannula and the outer cannula, which can provoke a blocking of the translation movement. The known device has also the inconvenient that, due to the presence of a double cannula, i.e. an inner cannula sliding within an outer cannula, the diameter of the cannula is relatively high. If one wishes to reduce the diameter of the outer cannula for allowing to access more easily within the body of the patient, the diameter of the inner cannula will also be reduced, which reduces the fat suction flow.
Another liposuction device is described in U.S. Pat. No. 5,352,194. The drive member of this device is provided for producing a translation movement having an amplitude of at least 1 cm. Such an amplitude produces a scrape effect which is dangerous since the user risks to exceed the limits of the region to be liposucked and injures in this way the patient. Furthermore, the larger the amplitude, the larger the reaction will be, which continuously provokes the back motion of the user""s wrist and reduces in this way the precision of the accomplished work.
Another liposuction device is described in patent application FR 2,691,624. This device is an ultrasound device, wherein the drive member is provided for producing a vibration movement at ultrasound frequency. Such a device turned out to be not very efficient, since the vibration movement at ultrasound frequency has to dispose the fat cells for subsequent suction. This technique is very slow. In addition, serious burns and cutaneous necrosis can occur.
The object of the present invention is to realise a liposuction device the use of which causes considerably less damage on the vessels and nerves, while achieving a mechanical assistance which allows to remove efficiently subcutaneous fat of the patient.
To this object, the liposuction device according to the invention is characterized in that the movement of the cannula is a nutation movement comprising vibration component perpendicular to the axis of the cannula and a translation component according to the axis of the cannula, wherein the translation component has an amplitude less than 1 cm.
The transmission of such nutation movement to the cannula has a double effect. On the one hand, the vibration component allows the cannula to perform a vibration movement when the latter is situated in the subcutaneous fat tissue. This movement will induce a vibration in the fat, allowing to easily introduce the fat in the cannula. On the other hand, the translation component amplifies the vibration component and insures in this way an efficient liposuction. The translation movement allows also to progress very easily and more smoothly the cannula within the skin of the patient. Limiting the amplitude of the translation component to a value less then 1 cm, the fat can easily be sucked in within its expansion limit while limiting considerably the risk to exceed the zone to be treated. The movement transmitted by the drive member creates a sinusoidal wave which extends along the cannula provoking a nutation force which contributes to dislocate the fat and to realize a real emulsion of the fatty tissue.
It has been established during experiments that a little amount of blood was extracted through the cannula, clearly indicating that the liposuction performed with the device according to the invention considerably limits vessels and nerves lesions compared to known devices with mechanical assistance, wherein there is either a guillotine effect or a scrape effect, or an inefficient liposuction. A local aneasthesia is therefore sufficient. Due to the absence of two cannulas sliding within one another, the diameter of the cannula introduced under the skin of the patient can be relatively limited, allowing to access more easily to zones of the human body having a relatively restricted access, such as the chin and the ankle, and limits furthermore the dimensions of scars formed on the skin of the patient.
In a first preferred embodiment of a device according to the invention, said movement produced by the drive member has a frequency between 10 and 500 Hz, preferably less than 250 Hz and most preferably approximately equal to 15 Hz. It has been found that such a frequency range allows to obtain efficient results in combination with the translation movement having an amplitude of less than 1 cm.
In a second preferred embodiment, the device according to the invention comprises a handle wherein said drive member is housed. This facilitates handling of the device according to the invention.
Preferably, the device comprises in addition a control member provided to control starting and stopping the drive member. In particular, the control member is a switch housed in said handle, or is formed by a control pedal cooperating with said drive member. The user can in this way easily control starting and stopping the device, in particular by controlling and holding the device with the same hand or by controlling the device by means of one of his feet.
Preferably said drive member is provided for functioning with compressed air and comprises a pneumatic piston for producing a backward and forward motion. The use of compressed air allows to realize a device which is easy to sterilize.
In another preferred embodiment of the liposuction device according to the invention, the device comprises in addition a cavity for a thumb, said cavity and said aperture being positioned on either side of the cannula axis. This embodiment allows the entry aperture to be directed towards the depth of fatty tissue and not towards the skin of the patient when the operator has introduced the cannula under the skin of a patient and has placed his thumb within the cavity.